Nokea
Which type of muscle is characterized by voluntary control and is responsible for body movement?
- A. Cardiac muscle
- B. Smooth muscle
- C. Skeletal muscle
- D. Connective tissue
Correct Answer: C
Rationale: The correct answer is skeletal muscle. Skeletal muscle is characterized by voluntary control, meaning it is under conscious control. It is responsible for body movement, such as walking, running, and lifting objects. Cardiac muscle is involuntary and found in the heart, while smooth muscle is also involuntary and found in organs like the intestines. Connective tissue is not a type of muscle but rather a type of tissue that provides support and structure in the body.
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What is the main function of vacuoles in plant cells?
- A. To provide structural support for the cell
- B. To transport substances in and out of the cell
- C. To synthesize proteins and lipids
- D. To store water, enzymes, and waste products
Correct Answer: D
Rationale: Vacuoles in plant cells primarily function as storage organelles. They store water, enzymes, pigments, and waste products, helping to maintain turgor pressure within the cell. This turgor pressure provides structural support for the plant cell. While vacuoles can also participate in transporting substances within the cell, their main role is storage. The synthesis of proteins and lipids is mainly handled by other organelles such as the endoplasmic reticulum and Golgi apparatus. Choice A is incorrect because while vacuoles indirectly contribute to structural support by maintaining turgor pressure, their primary function is storage. Choice B is incorrect as vacuoles are not primarily responsible for transporting substances in and out of the cell. Choice C is incorrect as vacuoles do not synthesize proteins and lipids; this function is carried out by other organelles.
Which enzyme found in saliva is responsible for breaking down carbohydrates into smaller molecules like sugars?
- A. Pepsin
- B. Amylase
- C. Lipase
- D. Trypsin
Correct Answer: B
Rationale: The correct answer is B. Saliva contains an enzyme called amylase, which specifically targets carbohydrates and breaks them down into smaller molecules like sugars. Pepsin, choice A, is an enzyme found in the stomach that breaks down proteins, not carbohydrates. Lipase, choice C, is responsible for breaking down fats, not carbohydrates. Trypsin, choice D, is an enzyme that breaks down proteins in the small intestine, not carbohydrates. Therefore, choices A, C, and D are incorrect for this question.
The Minimum Inhibitory Concentration (MIC) of an antibiotic refers to:
- A. The lowest concentration that kills bacteria
- B. The dose required for 50% bacterial inhibition
- C. The time it takes for an antibiotic to work
- D. The spectrum of bacteria the antibiotic targets
Correct Answer: B
Rationale: A) The lowest concentration that kills bacteria is known as the Minimum Bactericidal Concentration (MBC), not the Minimum Inhibitory Concentration (MIC). MIC is the lowest concentration of an antibiotic that inhibits visible growth of bacteria.
B) The MIC of an antibiotic is the concentration at which bacterial growth is inhibited by 50%. This concentration is used to determine the effectiveness of an antibiotic against a specific bacterium.
C) The time it takes for an antibiotic to work is not described by the MIC. MIC is a measure of concentration, not time.
D) The spectrum of bacteria the antibiotic targets is not defined by the MIC. The MIC value is specific to a particular antibiotic and bacterium, regardless of the spectrum of activity of the antibiotic.
Which part of the brainstem controls heart rate and breathing?
- A. Medulla oblongata
- B. Pons
- C. Midbrain
- D. Thalamus
Correct Answer: A
Rationale: The medulla oblongata is a critical part of the brainstem responsible for regulating essential functions such as heart rate, breathing, and blood pressure. It houses centers that oversee these involuntary processes, making it the correct answer. The pons, midbrain, and thalamus do not primarily control heart rate and breathing, thus making them incorrect choices for this question.
Molecular clocks utilize the accumulation of mutations in DNA sequences to estimate the evolutionary divergence time between species. This method relies on the assumption that:
- A. The rate of mutation is constant across all genes and all species.
- B. Species with more morphological similarities diverged more recently.
- C. Mutations are always beneficial and contribute to increased fitness.
- D. The fossil record provides the most accurate estimates of evolutionary relationships.
Correct Answer: A
Rationale: A molecular clock is a method used to estimate the time of divergence between species by measuring the accumulation of mutations in DNA sequences. This method relies on the assumption that mutations occur at a relatively constant rate over time. If the rate of mutation were not constant, it would be challenging to accurately estimate the evolutionary divergence time between species. Therefore, option A is the most appropriate choice as it aligns with the fundamental principle underlying the molecular clock hypothesis.
Option B is incorrect because the assumption that species with more morphological similarities diverged more recently does not directly relate to the concept of molecular clocks and the accumulation of mutations in DNA sequences.
Option C is incorrect because mutations are not always beneficial and do not always contribute to increased fitness. Mutations can be neutral or deleterious as well, and their accumulation is what is used to estimate evolutionary di